Golf ball incorporating tie layer between differing adjacent layers

ABSTRACT

A golf ball having improved adhesion comprising: a core; a first layer surrounding the core; a tie layer surrounding at least a portion of an outer surface of the first layer and consisting of a mixture of a polyfunctional aziridine compound and a solvent; and a second layer that is different than the first layer formed about the tie layer. The first layer may consist of a non-urethane composition whereas the second layer consists of at least one urethane composition. The first layer may comprise a non-urethane composition whereas the second layer consists of at least one urethane composition. The first layer may consist of a non-urethane composition while the second layer comprises a urethane composition. The first layer may comprise an ionomer for example. The solvent may be aprotic. Alternatively, the solvent may be protic.

FIELD OF THE INVENTION

The present invention relates to durable golf balls possessing excellent adhesive strength between differing adjacent layers (i.e., layers having different chemical and/or physical properties).

BACKGROUND OF THE INVENTION

Golf balls are made in a variety of constructions and compositions. In this regard, each of the golf ball core, intermediate layer, and cover may be single layered or comprise multiple layers. Examples of golf ball materials range from balata to polybutadiene, ionomer resins, polyurethanes, and/or polyureas. Typically, outer layers are formed about the spherical outer surface of an inner golf ball component via compression molding, casting, or injection molding.

Golf ball manufacturers continuously experiment with golf ball constructions and material formulations in order to target and improve aerodynamic and/or inertial properties and achieve desired feel without sacrificing durability. In this regard, the adhesion that exists between golf ball layers is essential in achieving adequate impact durability. Without a satisfactory amount of adhesion between these layers, both the impact durability as well as the shear resistance of the cover can be deemed as unacceptable.

This issue sometimes arises, for example, in preparing solid multilayer balls when materials of an outer layer do not necessarily bond well with the materials used in the inner layers, especially when two adjacent golf ball layers are formed from different compositions—e.g., an ionomeric casing/intermediate layer surrounded by a polyurethane cover layer. In such constructions, bond strength or “adhesive strength” between the two differing adjacent layers may be insufficient.

Poor bond or adhesive strength can result in layer separation or “delamination” when the golf ball is struck by a club. Layer separation may be visually apparent as “bubbling” or air pockets between the two layers. Delamination detrimentally affects not only the appearance of the golf ball but playability as well.

Thus, golf ball manufacturers look for cost effective compounds and methods for eliminating this problem in order to preserve brand recognition and reputation. Previous techniques/compounds for improving adhesive strength between adjacent, differing layers include plasma, corona discharge, silane, chlorination, and dispersion based mixtures of a resin (polyurethane, acrylic, polyurethane/acrylic combination, and/or polyurethane/urea combination) with an aziridine and water.

A significant limitation with techniques such as the corona and plasma treatments, however, is that a newly reactive treated surface rapidly reverts back to its normal state when re-exposed to air if the outer layer is not assembled about the treated surface immediately following treatment. Meanwhile, dispersion/resin-based adhesion promoters with aziridine and water are at least three-part mixtures.

Thus, there is a need for golf balls and manufacturing methods incorporating adhesion-promoting compounds which facilitate excellent adhesive strength between adjacent differing incompatible golf ball components without the limitations of prior adhesion-promoting techniques/compounds. The present invention addresses and solves these needs.

SUMMARY OF THE INVENTION

Accordingly, a golf ball of the invention having improved adhesion between two adjacent different layers comprises: a core; a first layer surrounding the core; a tie layer surrounding at least a portion of an outer surface of the first layer and consisting of a mixture of a polyfunctional aziridine compound and a solvent; and a second layer that is different than the first layer formed about the tie layer.

In one embodiment, the solvent is an aprotic solvent such as at least one of acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), and methyl isobutyl ketone. In another embodiment, the solvent may be a protic solvent such as water.

In one embodiment, the first layer consists of a non-urethane composition and the second layer consists of at least one urethane composition. For example, the non-urethane composition may comprise an ionomer.

In an alternative embodiment, the first layer consists of a non-urethane composition and the second layer comprises at least one urethane composition. In yet another embodiment, the first layer comprises a non-urethane composition and the second layer consists of at least one urethane composition. In any of these embodiments, the core may comprise polybutadiene, for example, although it is contemplated that any core material known in the golf ball art may be used in a golf ball of the invention.

The polyfunctional aziridine compound and the solvent may be mixed in a wt % ratio of from about 1:199 to about 1:19. In one particular embodiment, the polyfunctional aziridine compound and the solvent are mixed in a wt % ratio of about 1:49.

In another embodiment, the mixture consists of the aziridine compound in an amount of from about 0.5% to about 5% of the mixture. In yet another embodiment, the mixture consists of the aziridine compound in an amount of from about 1.0% to about 3% of the mixture.

In one embodiment, the mixture consists of the solvent in an amount of from about 99.5% to about 95% of the mixture.

In one embodiment, the outer surface is functionalized by the tie layer. Meanwhile, the second layer may have an average NCO functionality in the range of about 1.5 to 4.

The tie layer in one embodiment surrounds the entire outer surface of the first layer. In another embodiment, the tie layer surrounds a portion of the outer surface of the first layer (less than the entire outer surface). Additionally, embodiments are envisioned wherein at least one of the first layer and the second layer may be at least one of opaque, transparent and translucent.

Meanwhile, a golf ball of the invention may be formed from the steps comprising: providing a tie layer composition consisting of a mixture of a polyfunctional aziridine compound and a solvent; providing a core surrounded by a first golf ball layer comprising a non-urethane composition and having an outer surface; exposing the outer surface to the tie layer composition and forming a tie layer about at least a portion of the outer surface; and forming a second golf ball layer consisting of a urethane composition about the tie layer. In this construction, embodiments are also envisioned wherein at least one of the non-urethane composition of first golf ball layer and the urethane composition of the second golf ball layer is replaced/substituted with an alternative golf ball composition known in the art for casing and cover layers as long as the first and second golf ball layers are different and/or incompatible.

Additionally, the invention relates to a method of making a golf ball of the invention, comprising: providing a tie layer composition formed from mixing a polyfunctional aziridine compound and a solvent; providing a core surrounded by a first golf ball layer comprising a non-urethane composition and having an outer surface; exposing at least a portion of the outer surface to the tie layer composition and forming a tie layer about at least a portion of the outer surface; and forming a second golf ball layer consisting of a urethane composition about the tie layer. During forming the second golf ball layer about the tie layer, functional groups of the tie layer react with free isocyanates of the outer surface. Again, embodiments are also envisioned wherein at least one of the first golf ball layer and the second golf ball layer may be formed from other/alternative suitable materials as long as the first and second golf ball layers differ in some way such as with respect to their chemical and/or physical properties.

In one embodiment, the step of exposing the outer surface to the tie layer composition may comprise at least one process step selected from the group consisting of dipping, soaking, rolling, wiping, spraying, coating, brushing, and dusting. Further, the second golf ball layer may be formed about the tie layer during a molding process selected from the group consisting of compression molding; injection molding; and casting.

DETAILED DESCRIPTION

A golf ball of the invention possesses both excellent peel strength between adjacent differing layers and great shear resistance as demonstrated in TABLES I and II below, respectively. In this regard, golf ball Ex. 1 of TABLE I and golf ball Ex. 2 of TABLE II have identical constructions and formulations except that the cover of golf ball Ex. 1 is white pigmented, whereas the cover of golf ball Ex. 2 is clear and non-pigmented. The cover of golf ball Ex. 2 is clear and non-pigmented in order to facilitate visual inspection of golf ball Ex. 2 for incidence of delamination. Otherwise, the covers of both golf balls Ex. 1 and Ex. 2 incorporate the same polyurethane resin formed from a blend of Desmodur N and Desmodur N-3400; PTMEG 2000; and Ethacure 100-LC curative.

Meanwhile, golf balls Ex. 1 and Ex. 2 also comprise the same polybutadiene-based core having an outer diameter of 1.550 inches and the same compression of 80-90; a casing layer formed from an ionomer resin blend (50% Surlyn® 7940/50% Surlyn® 8940) and having an outer diameter of about 1.62 in., and a thickness of 0.035 in. Surlyn®7940 and Surlyn®8940 are ionomer resins available from Dupont.

Comparative golf balls Comp. Ex. 1 and Comp. Ex. 2 of TABLE I differ from golf ball Ex. 1 only at the interface or boundary between the casing layer and the cover layer. In particular, golf ball Ex. 1 uniquely includes tie layer L_(T) formed from a mixture of a polyfunctional aziridine compound and acetone in a wt. % ratio of 2:98, being resin-free. The polyfunctional aziridine compound used is CX-100 available from DSM Coating Resins LLC.

Tie layer L_(T) was formed about the entire outer surface of the casing layer of golf ball Ex. 1 by dipping the cased core into the mixture prior to forming the second layer thereabout. Tie layer L_(T) interacted with both the casing layer and the cover layer materials at an interface there between.

In contrast, in golf ball Comp. Ex. 1, the cover layer surrounds the casing layer, being in direct contact therewith when the cover is formed about the casing layer without any tie layer therebetween. And in golf ball Comp. Ex. 2, the cover layer surrounds and is adhered to a Corona treated outer surface of the casing layer rather than a tie layer. Corona discharge, well known by those of ordinary skill in the art, typically involves an electrical discharge that causes oxygen or other gas molecules within the discharge area to break into their atomic form, leaving them free to bond onto molecules on the surface of the treated article. See, e.g., U.S. Pat. Nos. 6,609,982, 5,466,424 (corona discharge surface treating method) and Stobbe, Bruce, “Corona Treatment 101,” Label and Narrow Web Indus., May-June, 1996, the entireties of each are hereby incorporated by reference herein.

Accordingly, golf balls Ex. 1, Comp. Ex. 1 and Comp. Ex. 2 were each rated with respect to peel strength. Peel strength was evaluated via the following physical Peel Test in order to determine the amount of adhesion of one layer to an adjacent layer. Specifically, the peel strength from cover layer to adjacent casing layer was evaluated on each of the three balls Ex. 1, Comp. Ex. 1 and Comp. Ex. 2 by performing the Peel Test. In particular, a strip of approximately ½ inch was cut around an equator of the golf ball, deep enough to cut through the entire layer to be tested. Next, a perpendicular cut was made across the strip and one end of the strip was peeled back just enough to make a tab of about ½ inch. The ball is then clamped into a jig by poles with the tab facing upward. The jig allows the clamped ball to freely rotate about an axis parallel to the poles. The tab is then clamped to a 20 lb. load cell of a universal testing machine. The tab is pulled away from the ball at a rate of 0.5 in./min., and the force required to pull the outer layer off of the underlying layer is recorded.

As is shown in TABLE I below, golf ball Ex. 1 has an excellent peel strength of 33.4 lbs./in., desirably quite higher than that of both golf ball Comp. Ex. 1 (peel strength of 5 lbs./in.) and golf ball Comp. Ex. 2 (peel strength of 20.6 lbs./in.). That is, the peel strength of golf ball Ex. 1 was found to be about 86% higher than the peel strength of golf ball Comp. Ex. 2, and about 38% greater than that of golf ball Comp. Ex. 2. Accordingly, while the Corona surface treatment improved adhesion as compared with no treatment at all, the two-part mixture of tie layer L_(T) substantially improved adhesive strength at the interface/boundary between the casing layer and cover layer over the Corona treatment.

TABLE I EXAMPLES Golf Ball Golf Ball Golf Ball Test Procedure Measurements Ex. 1 Comp. Ex. 1 Comp. Ex. 2 Peel Strength Peel Strength 33.4 5.4 20.6 (lbs./in.) Total Energy 222 13.4 85 (in. * lbs.) Peak Load 19.5 5.7 12.4 (lb. * ft.)

In turn, referring to TABLE II below, golf ball Ex. 2 and golf ball Comp. Ex. 3 differ only in that golf ball Ex. 2 incorporates a tie layer L_(T), whereas in golf ball Comp. Ex. 3, the cover layer surrounds and is adhered to a Corona treated outer surface of the casing layer. Golf balls Ex. 2 and Comp. Ex. 3 were rated with respect to incidence of delamination failure. Delamination failure presents visibly on the golf ball outer surface, often as a hazy white appearance due to an air pocket forming between the outer and underlying layer when the golf ball is struck by a club face. As mentioned above, a clear non-pigmented cover aids this visual inspection. First, 36 golf balls Ex. 2 and 36 golf balls Comp. Ex. 3 were soaked in water for 7 days to condition. Following conditioning, each of the 72 golf balls were removed from the water and shot from an air cannon at approximately 135 ft./sec. into a grooved plate at an angle of about 35° from horizontal. All 72 golf balls were subsequently examined for any delamination of the cover from the casing layer.

TABLE II reveals that none of the 36 golf balls Ex. 2 visually failed. Meanwhile, 15 of the 36 or about 41% of the golf balls Comp. Ex. 2 did visually fail:

TABLE II EXAMPLES Golf Ball Golf Ball Test Procedure Measurements Ex. 2 Comp. Ex. 3 Visual Failure of Number of balls 36 36 Water Soaked Golf hit Balls after Impact Number of 0 15 Failures

Accordingly, it is evident that a golf ball of the invention, incorporating a resin-free tie layer consisting of a two-part mixture of a polyfunctional aziridine compound and a solvent between two adjacent different and/or incompatible layers possesses superior adhesive strength at the boundary/interface between those two layers and the golf ball's durability is superior.

The example above is for illustrative purposes only and should not be construed as limiting the present invention in any way.

For example, embodiments are also envisioned wherein the polyfunctional aziridine and solvent may be mixed in weight % ratios of from about 1:199 to about 1:19, or from about 1:49 to about 1:24, or from about 1:99 to about 1:24, or from about 1:24 to about 1:19, or from about 1:199 to about 1:49.

Additionally, while tie layers L_(T) of golf balls EX. 1 and EX. 2 include a mixture of polyfunctional aziridine and solvent in relative weight percents of 2 and 98, respectively, in other embodiments, the mixture may consist of the aziridine compound and solvent in relative amounts of from about 1% to about 4% and from about 99% to about 96% of the mixture, respectively. In still another embodiment, the mixture may consist of the aziridine compound and solvent in relative amounts of from about 2% to about 3% and from about 98% to about 97% of the mixture, respectively.

Moreover, the tie layer may be applied to and surround the entire outer surface of the first layer, or be provided on only a portion thereof. For example, in one embodiment, the tie layer may be applied onto from about 50% to about 90% of the first layer's outer surface. In other embodiments, the tie layer may be applied onto less than 100% of the first layer's outer surface.

Numerous methods or procedures are known in the art for providing/forming a tie layer between adjacent differing/incompatible golf ball layers. In a golf ball of the invention, the tie layer mixture may be provided, for example, by dipping, soaking, rolling, wiping, spraying, coating, brushing, dusting or otherwise treating or exposing the outer surface of the first or innermost layer with/to the tie layer composition followed by forming the second or outermost layer about, and adjacent to, the first layer.

Advantageously, in a golf ball and/or method of the invention, the tie layer mixture may be applied or otherwise provided about the first layer at any time including during the molding process for forming the first layer itself and up to and including when the second layer is formed about the first layer. Of course, embodiments are also envisioned wherein the mixture is formed onto an inner surface of the second layer sometime prior to being formed about the first layer—e.g., where the second layer is a molded part.

In a different embodiment, the golf ball may comprise a core; a first layer surrounding the core; a tie layer surrounding at least a portion of an outer surface of the first layer and consisting of a mixture of a polyfunctional aziridine compound; a solvent; and at least one of: a solvent borne urea, one or more isocyanates, an acid copolymer solution, and/or a high acid composition; surrounded by a second layer that is different than and/or incompatible with the first layer. In an alternative embodiment, the tie layer consists of a mixture of a polyfunctional aziridine compound; a solvent; and one of: (i) one or more isocyanates; (ii) an acid copolymer solution; and (iii) a high acid composition. In an further embodiment, the tie layer consists of a mixture of a polyfunctional aziridine compound; a solvent; and two of: (i) one or more isocyanates; (ii) an acid copolymer solution; and (iii) a high acid composition. In each of these embodiments, the tie layer may be applied to the entire outer surface of the first layer, or, in other embodiments, be applied to only a portion of the outer surface of the first layer.

In a further embodiment, the tie layer may consist of a mixture of an acid copolymer and a solvent. In one such embodiment, the solvent may comprise THF, for example.

A golf ball of the invention incorporating a tie layer may otherwise have any known construction as long as the tie layer is positioned between two adjacent layers that are formed form different compositions or are incompatible in that they bond together poorly. In one embodiment, a golf ball of the invention has a rubber containing core, wherein the base rubber may be selected from polybutadiene rubber, polyisoprene rubber, natural rubber, ethylene-propylene rubber, ethylene-propylene diene rubber, styrene-butadiene rubber, and combinations of two or more thereof. A preferred base rubber is polybutadiene. Another preferred base rubber is polybutadiene optionally mixed with one or more elastomers selected from polyisoprene rubber, natural rubber, ethylene propylene rubber, ethylene propylene diene rubber, styrene-butadiene rubber, polystyrene elastomers, polyethylene elastomers, polyurethane elastomers, polyurea elastomers, metallocene-catalyzed elastomers, and plastomers.

Suitable curing processes include, for example, peroxide curing, sulfur curing, radiation, and combinations thereof. In one embodiment, the base rubber is peroxide cured. Organic peroxides suitable as free-radical initiators include, for example, dicumyl peroxide; n-butyl-4,4-di(t-butylperoxy) valerate; 1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane; 2,5-dimethyl-2,5-di(t-butylperoxy) hexane; di-t-butyl peroxide; di-t-amyl peroxide; t-butyl peroxide; t-butyl cumyl peroxide; 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3; di(2-t-butyl-peroxyisopropyl)benzene; dilauroyl peroxide; dibenzoyl peroxide; t-butyl hydroperoxide; and combinations thereof. Peroxide free-radical initiators are generally present in the rubber compositions in an amount within the range of 0.05 to 15 parts, preferably 0.1 to 10 parts, and more preferably 0.25 to 6 parts by weight per 100 parts of the base rubber. Cross-linking agents are used to cross-link at least a portion of the polymer chains in the composition. Suitable cross-linking agents include, for example, metal salts of unsaturated carboxylic acids having from 3 to 8 carbon atoms;

unsaturated vinyl compounds and polyfunctional monomers (e.g., trimethylolpropane trimethacrylate); phenylene bismaleimide; and combinations thereof. Particularly suitable metal salts include, for example, one or more metal salts of acrylates, diacrylates, methacrylates, and dimethacrylates, wherein the metal is selected from magnesium, calcium, zinc, aluminum, lithium, and nickel. In a particular embodiment, the cross-linking agent is selected from zinc salts of acrylates, diacrylates, methacrylates, and dimethacrylates. When the cross-linking agent is zinc diacrylate and/or zinc dimethacrylate, the agent typically is included in the rubber composition in an amount within the range of 1 to 60 parts, preferably 5 to 50 parts, and more preferably 10 to 40 parts, by weight per 100 parts of the base rubber.

In a preferred embodiment, the cross-linking agent used in the rubber composition of the core and epoxy composition of the intermediate layer and/or cover layer is zinc diacrylate (“ZDA”). Adding the ZDA curing agent to the rubber composition makes the core harder and improves the resiliency and COR of the ball. Adding the same ZDA curing agent epoxy composition makes the intermediate and cover layers harder and more rigid. As a result, the overall durability, toughness, and impact strength of the ball is improved.

Sulfur and sulfur-based curing agents with optional accelerators may be used in combination with or in replacement of the peroxide initiators to cross-link the base rubber. High energy radiation sources capable of generating free-radicals may also be used to cross-link the base rubber. Suitable examples of such radiation sources include, for example, electron beams, ultra-violet radiation, gamma radiation, X-ray radiation, infrared radiation, heat, and combinations thereof.

The rubber compositions may also contain “soft and fast” agents such as a halogenated organosulfur, organic disulfide, or inorganic disulfide compound. Particularly suitable halogenated organosulfur compounds include, but are not limited to, halogenated thiophenols. Preferred organic sulfur compounds include, but not limited to, pentachlorothiophenol (“PCTP”) and a salt of PCTP. A preferred salt of PCTP is ZnPCTP. A suitable PCTP is sold by the Struktol Company (Stow, Ohio) under the tradename, A95. ZnPCTP is commercially available from EchinaChem (San Francisco, Calif.). These compounds also may function as cis-to-trans catalysts to convert some cis-1,4 bonds in the polybutadiene to trans-1,4 bonds. Peroxide free-radical initiators are generally present in the rubber compositions in an amount within the range of 0.05 to 10 parts and preferably 0.1 to 5 parts. Antioxidants also may be added to the rubber compositions to prevent the breakdown of the elastomers. Other ingredients such as accelerators (for example, tetra methylthiuram), processing aids, processing oils, dyes and pigments, wetting agents, surfactants, plasticizers, as well as other additives known in the art may be added to the composition. Generally, the fillers and other additives are present in the rubber composition in an amount within the range of 1 to 70 parts by weight per 100 parts of the base rubber. The core may be formed by mixing and forming the rubber composition using conventional techniques. Of course, embodiments are also envisioned wherein outer layers comprise such rubber-based compositions

Cores, intermediate/casing layers, and cover layers may be formed from an ionomeric material including ionomeric polymers, preferably highly-neutralized ionomers (HNP). In another embodiment, the intermediate layer of the golf ball is formed from an HNP material or a blend of HNP materials. The acid moieties of the HNP's, typically ethylene-based ionomers, are preferably neutralized greater than about 70%, more preferably greater than about 90%, and most preferably at least about 100%. The HNP's can be also be blended with a second polymer component, which, if containing an acid group, may also be neutralized. The second polymer component, which may be partially or fully neutralized, preferably comprises ionomeric copolymers and terpolymers, ionomer precursors, thermoplastics, polyamides, polycarbonates, polyesters, polyurethanes, polyureas, thermoplastic elastomers, polybutadiene rubber, balata, metallocene-catalyzed polymers (grafted and non-grafted), single-site polymers, high-crystalline acid polymers, cationic ionomers, and the like. HNP polymers typically have a material hardness of between about 20 and about 80 Shore D, and a flexural modulus of between about 3,000 psi and about 200,000 psi.

Non-limiting examples of suitable ionomers include partially neutralized ionomers, blends of two or more partially neutralized ionomers, highly neutralized ionomers, blends of two or more highly neutralized ionomers, and blends of one or more partially neutralized ionomers with one or more highly neutralized ionomers. Methods of preparing ionomers are well known, and are disclosed, for example, in U.S. Pat. No. 3,264,272, the entire disclosure of which is hereby incorporated herein by reference. The acid copolymer can be a direct copolymer wherein the polymer is polymerized by adding all monomers simultaneously, as disclosed, for example, in U.S. Pat. No. 4,351,931, the entire disclosure of which is hereby incorporated herein by reference. Alternatively, the acid copolymer can be a graft copolymer wherein a monomer is grafted onto an existing polymer, as disclosed, for example, in U.S. Patent Application Publication No. 2002/0013413, the entire disclosure of which is hereby incorporated herein by reference.

Any golf ball component, namely core, intermediate layer, cover, etc. may also be formed from or comprise or include or be blended or otherwise combined or mixed with any of the following compositions as known in the art to achieve particular desired golf ball characteristics:

-   -   (1) Polyurethanes, such as those prepared from polyols and         diisocyanates or polyisocyanates and/or their prepolymers, and         those disclosed in U.S. Pat. Nos. 5,334,673 and 6,506,851;     -   (2) Polyureas, such as those disclosed in U.S. Pat. Nos.         5,484,870 and 6,835,794; and     -   (3) Polyurethane-urea hybrids, blends or copolymers comprising         urethane and urea segments.

Suitable polyurethane compositions comprise a reaction product of at least one polyisocyanate and at least one curing agent. The curing agent can include, for example, one or more polyols. The polyisocyanate can be combined with one or more polyols to form a prepolymer, which is then combined with the at least one curing agent. Thus, the polyols described herein are suitable for use in one or both components of the polyurethane material, i.e., as part of a prepolymer and in the curing agent. Suitable polyurethanes are described in U.S. Pat. No. 7,331,878, which is incorporated herein in its entirety by reference.

Examples of yet other materials which may be suitable for incorporating and coordinating in order to target and achieve desired playing characteristics or feel include plasticized thermoplastics, polyalkenamer compositions, polyester-based thermoplastic elastomers containing plasticizers, transparent or plasticized polyamides, Thiol-ene compositions, polyamide and anhydride-modified polyolefins, organic acid-modified polymers, and the like.

Meanwhile, the dimensions of each golf ball component such as the diameter of the core and respective thicknesses of the intermediate layer (s), cover layer(s) and coating layer(s) may be selected and coordinated as known in the art for targeting and achieving desired playing characteristics or feel. For example, the core may have a diameter of from about 1.47 inches (in.) to about 1.62 in.; the intermediate/casing layer may have a thickness of from about 0.025 in. to about 0.057 in.; a core and intermediate/casing layer, combined, may have a diameter of from about 1.57 in. to about 1.65 in.; the cover may have a thickness of from about 0.015 in. to about 0.055 in.; and any coating layers may have a combined thickness of from about 0.1 μm to about 100 μm, or from about 2 μm to about 50 μm, or from about 2 μm to about 30 μm. Meanwhile, each coating layer may have a thickness of from about 0.1 μm to about 50 μm, or from about 0.1 μm to about 25 μm, or from about 0.1 μm to about 14 μm, or from about 2 μm to about 9 μm, for example.

As used herein, “indicia” is considered to mean any symbol, letter, group of letters, design, or the like, that can be added to the dimpled surface of a golf ball.

It will be appreciated that any known dimple pattern may be used with any number of dimples having any shape or size. For example, the number of dimples may be 252 to 456, or 330 to 392 and may comprise any width, depth, and edge angle. The parting line configuration of said pattern may be either a straight line or a staggered wave parting line (SWPL).

In any of these embodiments the single-layer core may be replaced with a 2 or more layer core wherein at least one core layer has a hardness gradient.

Other than in the operating examples, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for amounts of materials and others in the specification may be read as if prefaced by the word “about” even though the term “about” may not expressly appear with the value, amount or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used.

Although the golf ball of the invention has been described herein with reference to particular means and materials, it is to be understood that the invention is not limited to the particulars disclosed and extends to all equivalents within the scope of the claims. 

1. A golf ball having improved adhesion between two adjacent different layers, comprising: a core; a first layer formed from a first resin and having a thickness of at least 0.025 in. surrounding the core; a tie layer surrounding at least a portion of an outer surface of the first layer and consisting of a resin-free mixture of a polyfunctional aziridine compound and a solvent; and a second layer that is formed from a different resin than the first layer and has a thickness of at least 0.015 in. formed about the tie layer.
 2. The golf ball of claim 1, wherein the solvent is aprotic and comprises at least one of acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), and methyl isobutyl ketone.
 3. The golf ball of claim 1, wherein the solvent comprises water.
 4. The golf ball of claim 1, wherein the first layer comprises a non-urethane composition and the second layer consists of at least one urethane composition.
 5. The golf ball of claim 1, wherein the first layer consists of a non-urethane composition and the second layer comprises a urethane composition.
 6. The golf ball of claim 1, wherein the first layer consists of a non-urethane composition and the second layer consists of at least one urethane composition.
 7. The golf ball of claim 6, wherein the non-urethane composition comprises an ionomer.
 8. The golf ball of claim 6, wherein the second layer has an average NCO functionality in the range of about 1.5 to
 4. 9. The golf ball of claim 1, wherein the polyfunctional aziridine compound and the solvent are mixed in a wt % ratio of from about 1:199 to about 1:19.
 10. The golf ball of claim 1, wherein the polyfunctional aziridine compound and the solvent are mixed in a wt % ratio of about 1:49.
 11. The golf ball of claim 1, wherein the mixture consists of the aziridine compound in an amount of from about 0.5% to about 5% of the mixture.
 12. The golf ball of claim 1, wherein the mixture consists of the aziridine compound in an amount of from about 1.0% to about 3% of the mixture.
 13. The golf ball of claim 1, wherein the outer surface is functionalized by the tie layer.
 14. The golf ball of claim 1, wherein the tie layer surrounds the entire outer surface of the first layer.
 15. The golf ball of claim 1, wherein the tie layer surrounds a portion of the entire outer surface of the first layer.
 16. The golf ball of claim 1, wherein at least one of the first layer and the second layer is at least one of opaque, transparent and translucent.
 17. The golf ball of claim 1, wherein the core comprises polybutadiene. 